Field of the Invention
The invention relates to a housing for a motor vehicle HVAC system.
Description of the Background Art
HVAC systems for motor vehicles (such as, for example, passenger cars and commercial vehicles) are injection molded from plastic. The HVAC system housings are made as thin-walled hollow bodies. Because undercuts can be realized only conditionally in the plastic injection molding process, the housings are made of a number of parts, which are then assembled. In addition, components such as heat exchangers and flaps must be installed in the HVAC device, which would be possible only to a limited extent in a closed housing.
One-piece sealing systems in the form of a tongue-and-groove geometry are used in each case to seal the housing parts from one another. In other words, no additional material is used for the sealing.
This type of tongue-and-groove joint 10 known from the prior art, which connects housing parts 2, 3 of a housing 1 together, is illustrated in FIG. 1.
A groove-shaped geometry (groove) 20 is made in one housing part 2 and a tongue-shaped geometry (tongue) 30 in another housing part 3. This tongue-and-groove geometry 10 has in addition the task of being an installation aid, so that housing parts 2, 3 can be positioned readily and with an accurate fit to one another and assembled. The fixation of housing parts 2, 3 then occurs with metal clips or screws (not shown).
Groove 20 comprises two groove legs 40, 50, whereby groove leg 40 is disposed on the side of groove 20, said side facing housing interior 100, and groove leg 50 on the side of groove 20, said side facing housing exterior 200. In the inserted state of tongue 30 in groove 20 as shown in FIG. 1, the groove-side shoulders 41, 51 each lie on the corresponding tongue-side shoulders 31, 32. In FIG. 1, tongue 30 lies in the groove interior with its tongue flanks 35, 36.
The sealing principle of the tongue-and-groove joint 10 is primarily the supporting of the shoulder surfaces of the inner groove-side shoulder 41 and the outer groove-side shoulder 51. A labyrinth due to a tongue-and-groove joint 10 has a further but secondary sealing effect.
In the tongue-and-groove joint 10 illustrated in FIG. 1, both groove shoulders 41, 51 should be supported. This is rarely the case, however, because of fabrication tolerances. The sealing direction is the direction labeled Z. A direction perpendicular to the sealing direction Z is labeled X. The total width of the tongue-and-groove joint in this example is 5 mm, and the total height of the tongue-and-groove joint is 7.3 mm.
In this regard, the total width of tongue-and-groove joint 10 between side 33, facing housing interior 100, of tongue-side shoulder 31 and side 34, facing housing exterior 200, of tongue-side shoulder 32 is measured. The total height of tongue-and-groove joint 10 between side 26, facing away from tongue 30, of groove base 25 and side 37, facing away from groove 20, of tongue-side shoulder 32 is measured.
The groove legs (groove shoulders) 40, 50 are each 1.2 mm thick at the end. The bevel on the inner sides of both groove legs 40, 50 relative to the Z-direction is 2° in each case. The groove depth is 4.6 mm. The wall thickness of the housing wall, extending below tongue 30, of the tongue-side housing part is 1.8 mm. The tongue width is 2.4 mm at the bottom. The tongue height is 4.2 mm. The angle on the inner tongue side, i.e., the angle between the Z-direction and the inner tongue flank 35, and the angle on the outer tongue side, i.e., the angle between the Z-direction and tongue flank 36, are each also 2°. The distance between groove 20 and tongue 30 per side, i.e., the distance between one of the groove legs 40, 50 and tongue 30 is 0.1 mm in each case. Typically, wall thicknesses of the housing walls of 1.8 mm are used.
It is disadvantageous in the tongue-and-groove joints from the prior art that due to the fabrication tolerances in plastic injection-molded parts, primarily due to warping and shrinkage, the groove shoulder surfaces are not supported continuously. Often only a groove shoulder (groove flank) is supported, and the groove shoulder with support changes, for example, from outside to inside. Because air can flow transversely in the area of the tongue-and-groove joint, it exits in other areas. In part, there is also no contact at all of the groove-side shoulders to the tongue-side shoulders. Here air exits directly. This air leakage reduces the air output, which is available for climatizing the vehicle interior.
Furthermore, elastic tongue-and-groove systems, which comprise either an elastic tongue or an elastic groove, are known from the prior art. Systems with elastic tongues are described in the documents EP 1 510 380 B1 (which corresponds to U.S. Pat. No. 7,036,825), EP 0 414 946 B1, and DE 199 43 278 A1. Systems with an elastic groove are described in the documents DE 44 25 362 A1 and EP 2 284 27 A2. It is a disadvantage in such elastic tongue-and-groove systems that they have a lower elasticity in the region of radii. As a result, fabrication tolerances can no longer be compensated, which leads to increased leakage. Basically, elastic deformation also leads to higher assembly forces.
Tongue-and-groove systems with at least one undercut at the groove are also known from the prior art. Such tongue-and-groove systems are described, for example, in the documents DE 94 20 291 U1 and EP 2 284 27 A2. A disadvantage in such tongue-and-groove systems is that the assembly force is considerably increased. In addition, the production of the undercuts is associated with additional manufacturing costs.